Fluorescence light source devices each configured to radiate fluorescence from a phosphor when the phosphor is irradiated with laser light as excitation light have been known conventionally.
One type of such fluorescence light source devices includes: a wavelength conversion member including a fluorescence member 41 constituted by a phosphor; an excitation laser light source 46 for irradiating the wavelength conversion member with excitation light L; and a lens 48 for concentrating fluorescence L1 from the wavelength conversion member as shown in FIG. 6 (see, for example, Patent Literature 1). The wavelength conversion member is disposed on a light reflective substrate 49 via a bonding part 43. A front surface of the wavelength conversion member serves as an excitation light receiving surface as well as a fluorescence emission surface. In this fluorescence light source device 40, pores are contained in the wavelength conversion member, i.e., in the fluorescence member 41.
In fluorescence light source devices, a technique for forming a periodic structure on a front surface of a wavelength conversion member, serving as an excitation light receiving surface, in order to improve excitation light incidence efficiency in the wavelength conversion member has been known (see, for example, Patent Literature 2). Specifically, Patent Literature 2 discloses a fluorescence light source device including a wavelength conversion member including a plate-shaped fluorescence member and a generally plate-shaped light-transmissive member provided to cover a front surface and a peripheral surface of the fluorescence member. In this fluorescence light source device, the light-transmissive member is light-transmissive to excitation light and fluorescence generated in the fluorescence member. A periodic structure including a periodic array of projections is formed in a front surface of the wavelength conversion member, which serves as an excitation light receiving surface. Moreover, pores or scattering microparticles are contained in the light-transmissive member.
In such a fluorescence light source device, however, the excitation light and the fluorescence are scattered by the pores or the scattering microparticles, thereby failing to obtain sufficient fluorescence intensity.
Specifically speaking, part of excitation light having entered into the wavelength conversion member through the excitation light receiving surface is scattered by the pores or the scattering microparticles and allowed to exit to the outside through the excitation light receiving surface without being converted into fluorescence. Thus, the excitation light having entered into the fluorescence member cannot be utilized effectively, resulting in a reduction in an amount of fluorescence exiting through the fluorescence emission surface.